1 /*
2  * Copyright (C) 2015 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.example.android.rs.vr.engine;
18 
19 /**
20  * Some minimal utilities for Vector math
21  */
22 public class VectorUtil {
sub(double[] a, double[] b, double[] out)23     public static void sub(double[] a, double[] b, double[] out) {
24         out[0] = a[0] - b[0];
25         out[1] = a[1] - b[1];
26         out[2] = a[2] - b[2];
27     }
28 
mult(double[] a, double b, double[] out)29     public static void mult(double[] a, double b, double[] out) {
30         out[0] = a[0] * b;
31         out[1] = a[1] * b;
32         out[2] = a[2] * b;
33     }
34 
dot(double[] a, double[] b)35     public static double dot(double[] a, double[] b) {
36         return a[0] * b[0] + a[1] * b[1] + a[2] * b[2];
37     }
38 
norm(double[] a)39     public static double norm(double[] a) {
40         return Math.sqrt(a[0] * a[0] + a[1] * a[1] + a[2] * a[2]);
41     }
42 
cross(double[] a, double[] b, double[] out)43     public static void cross(double[] a, double[] b, double[] out) {
44         double out0 = a[1] * b[2] - b[1] * a[2];
45         double out1 = a[2] * b[0] - b[2] * a[0];
46         double out2 = a[0] * b[1] - b[0] * a[1];
47         out[0] = out0;
48         out[1] = out1;
49         out[2] = out2;
50     }
51 
normalize(double[] a)52     public static void normalize(double[] a) {
53         double norm = norm(a);
54         a[0] /= norm;
55         a[1] /= norm;
56         a[2] /= norm;
57     }
58 
add(double[] a, double[] b, double[] out)59     public static void add(double[] a, double[] b,
60                            double[] out) {
61         out[0] = a[0] + b[0];
62         out[1] = a[1] + b[1];
63         out[2] = a[2] + b[2];
64     }
65 
66 }
67